Williams, the star of "Mrs. Doubtfire," "Good Will Hunting" and "Dead Poets Society" as well as the television series that rocketed him to fame, "Mork & Mindy," hanged himself with a belt Monday, police said.

Ursone said it was hard to decide which performance was Williams' best - especially because his live impromptu appearances were often extraordinary works of art as well.

"His 'Inside the Actors Studio' session is legendary," Ursone said. "That unbelievable boundless energy is unparalleled. Literally there is no one else like him."

He said Williams was unique among actors and comedians.

"I don't think anyone, that I can think of, that had that boundless kinetic , frenetic brilliance," Ursone said.

Among the many spectacular movies that Williams made, Ursone said "Dead Poets Society" is his favorite, although he said "Good Morning, Vietnam" was notable because it combined Williams' frenetic, high-energy comedic style with serious acting.